Deformation characteristics of unsaturated slope during post-rainfall earthquake: Insights from centrifuge and numerical modeling

Slopes are likely to fail in areas with frequent rainfall and earthquakes. The deformation characteristics of unsaturated slopes subjected to post-rainfall earthquakes are investigated using centrifuge model tests and finite element analyses. Three tests of the slope deformation under earthquake and post-rainfall earthquakes are first studied using image analysis techniques. Then, based on an elastoplastic constitutive model, numerical simulations are carried out using the finite element method and compared with the centrifuge test results. Finally, a parametric study is performed to clarify the effects of antecedent rainfall on earthquake-induced slope deformation. The results show that slope deformation caused by post-rainfall earthquakes differs from that caused by earthquakes without antecedent rainfall. The seepage flow and soil strength of the slope are affected by previous rainfall conditions, such as intensity and duration, which directly influence the slope deformation caused by the subsequent earthquake. Soil displacement and strain become greater and the slip surface is more noticeable during the post-rainfall earthquake of higher intensity. In addition, the time interval between the rainfall and the earthquake has a considerable impact on the detailed characteristics of the slope deformation, and the significant deformation occurs at the time of lowest soil strength when seepage flow reaches the lower part of the slope. Moreover, the repeated intermittent rainfall greatly affects the subsequent earthquake-induced slope deformation, the main characteristics of which are closely related to the changes in saturation and strength of the slope. However, with the prolonged time gap between each round of rainfall, the earthquake-induced slope deformation becomes insignificant.